diff --git a/promgen/rest_v2.py b/promgen/rest_v2.py
index d764e51b..c7005c3c 100644
--- a/promgen/rest_v2.py
+++ b/promgen/rest_v2.py
@@ -764,6 +764,8 @@ def hosts(self, request, id):
     @hosts.mapping.post
     def register_host(self, request, id):
         farm = self.get_object()
+        if not farm.source == discovery.FARM_DEFAULT:
+            raise ValidationError({"detail": "Hosts can only be registered to local farms."})
         hostnames = request.data.get("hosts", [])
         valid_hosts = set()
         invalid_hosts = set()